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[in Japanese]
1997 Volume 10 Issue 6 Pages
513-514
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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Jun ASANUMA, Wilfried BRUTSAERT
1997 Volume 10 Issue 6 Pages
515-523
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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The variances of vertical velocity, w, temperature, θ, and humidity, q, that were observed in the atmospheric surface layer over a flat pine forest with an aircraft were analyzed on the basis of Monin-Obukhov similarity (MOS). The values of σw and σθ were found to obey closely the one-third power law, representing the asymptotic form of MOS under strongly unstable conditions, whereas σq was observed to display considerable scatter. This scatter can be attributed, in part, to the surface inhomogeneity, which resulted from the characteristics of the terrain, consisting of a mixture of forest stands and clearings. It was also shown that this surface inhomogeneity caused a breakdown of the similarity between scalars. On the basis of the one-third power law, three types of the variance method were applied to these variances in order to estimate surface fluxes. Comparison with the aircraft-measured surface fluxes indicated that some of the variance methods generate reasonable estimates of the sensible heat flux. For latent heat flux, the variance method could produce surface flux values comparable to the measurements, albeit with scatter, only when the constants involved were locally calibrated.
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(1) Estimation Method
Tetsu HASHIMOTO, Takeshi OHTA, Tsutomu NAKAMURA
1997 Volume 10 Issue 6 Pages
524-536
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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We proposed procedures for estimating the hourly value of the global solar radiation, downward long-wave radiation and snowmelt rates at any position in a forest, using the three dimensional distribution of the foliage density in about one hectare. The three dimensional distributions were reconstructed with the fisheye photographs. Results of the estimations are as follows: The estimated values of the global solar radiation in forests agreed well with the observed values under the leafless conditions. Under the leafed conditions, the direct solar radiation through gaps of the canopy was not reproduced satisfactorily. Estimated values of the downward long-wave radiation and snowmelt rates in the forests were close to the observed values. And we could conclude that the spacial variability of the daily global solar radiation, hourly downward long-wave radiation and daily snowmelt rates in the forests estimated by the procedures had good reproducibilities.
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Hiroshi ISHIDAIRA, Toshio KOIKE, Minjiao LU, Norio HAYAKAWA
1997 Volume 10 Issue 6 Pages
537-546
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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To incorporate land surface schemes into climate models adequately, a method for aggregation of hydrological processes on large area with heterogeneity, a macro-scale hydrological model, has to be developed. Shortwave radiation is one of the most important factor for land surface hydrological processes. Because of topographic variability on land surface, however, it is difficult to evaluate the incident solar radiation flux over land surface with undulation. This study present a method to calculate spatially averaged shortwave radiation flux on land surface with undulation. We use an “Insolation Receiving Rate (IRR)” at each slope for estimation of the effect of slope inclination and aspect, and propose a macro-scale IRR which expresses the variance of IRR in a large area in addition to the average value. Finally, we evaluate the effect of spatial variability of IRR on evaporation and snowmelt.
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Comparisons of evapotranspiration using surface temperature method, Bowen ratio method and eddy correlation method.
Nobuhiro EBISU, Shigeru OGAWA, Masakazu SUZUKI, Takafumi TANAKA
1997 Volume 10 Issue 6 Pages
547-556
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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The objective of this study is to make comparisons of estimated evapotranspiration using surface temperature method (ST method), Bowen ratio method and eddy correlation method. The ST method calculates evapotranspiration using image data of surface temperature and energy budget data at forested areas. The errors of averaged daily evapotraspiration by ST method at three study areas are from 2% to 12% by Bowen ratio method and 3% by eddy correlation method. The errors result from variations of surface temperature at canopies which are affected by the shadow of leaves, structure of trees and types of tree. Averaged differences of hourly sensible heat flux are from -35Wm-2 to 26Wm-2 by ST method and eddy correlation method. Estimated values of hourly evapotranspiration by ST method are roughly equal to those by Bowen ratio method and eddy correlation method up to about 0.6mm/hr and are smaller than those over about 0.7mm/hr.
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Yutaka ICHIKAWA, Yasuhiro SATOH, Yasuto TACHIKAWA, Michiharu SHIIBA
1997 Volume 10 Issue 6 Pages
557-570
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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Paddy field runoff models proposed until now are mainly classified into two groups: (1) models which simulate long-term runoff taking into account irrigation and drainage, but simplify the flood routing; (2) models which simulate short-term flood runoff taking into account the interaction caused by the overflow on a levee between a paddy field and a stream network. In this paper, we develop the new paddy field runoff model integrating the Complex Tank Model and the Diffusive Tank Model, which are representative models of each group, respectively. Then, we build the new paddy field runoff element model by using OHyMoS (Object-oriented Hydrological Modeling System), and apply it to Kizu River basin in Japan.
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Hideyuki NAGAI, Tetsuo KOBAYASHI, Ken SAHASHI
1997 Volume 10 Issue 6 Pages
571-576
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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At the HEIFE desert station established in the northwest of China, the humidity inversion was often observed in the surface air layer in the daytime; that is, water vapor density increased with height. Furthermore, it was verified by intensive observation that water vapor moved upward under the ground surface even during the humidity inversion, which means that the countergradient flow of water vapor occurred near the surface. It was also confirmed that this humidity inversion had close relations with a phenomenon that the water vapor density within the dry surface soil layer (DSL) and the surface air layer suddenly decreased when the ground surface temperature increased and exceeded the air temperature immediately above it by some threshold value.
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I. Indoor Experiment
Katumi MUSIAKE, Masahiro KOIKE, Taikan OKI, Tosiyuki NAKAEGAWA
1997 Volume 10 Issue 6 Pages
577-587
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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A C band microwave scatterometer was designed and made for soil moisture measurement in a indoor experiments. After some electromagnetic experiments, many experiments were carried out to clarify the basic characteristics of the soil backscatter from its surface. These experiments give the following results: (i) C band microwave penetrates the soil to 10 cm depth, (ii) 2.5cm depth surface soil sampling is optimum to regress the soil moisture with the backscatter coefficients, (iii) the backscatter coefficients are sensitive to the incident angle in less than 30°, (iv) HH polarization is more sensitive to the soil moisture than the HV polarization, (v) surface roughness has a significant effect on the soil backscatter.
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II. Outdoor Experiment
Katumi MUSIAKE, Tosiyuki NAKAEGAWA, Masahiro KOIKE, Taikan OKI
1997 Volume 10 Issue 6 Pages
588-596
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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A scatterometer mesuring system mounted on a car was designed for outdoor experiments and outdoor experiments using its system were carried out to compare the backscatter at different surface conditions of soil type, surface roughness, and vegetation. The results of these experiments were summarized as follows: (i) a portable C band scatterometer measuring system for the outdoor experiments was established, (ii) positive correlation between soil moisture and the backscatter was found at the incident angle of more than 30° but the coefficients decrease as the angle becomes larger, (iii) the relationship between the soil moisture and the backscatter is different from each sites respectively, on which the surface roughness and vegetation have a significant effect, (iv) the surface roughness has a more significant effect than the soil type.
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III. Verification Experiment of the Synthetic Aperture Radar mounted on Spaceborne Satellites
Katumi MUSIAKE, Taikan OKI, Tosiyuki NAKAEGAWA, Masahiro KOIKE
1997 Volume 10 Issue 6 Pages
597-606
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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Ground-base verification experiments for the soil moisture detection by spaceborne SARs (E ERS-1 and J ERS-1) were carried out. Backscattering coefficients obtained from satellite SARs were compared with those measured by ground-base scatterometer system and ground truth data of soil moisture, and the relationship between backscattering coefficients measured by SARs and soil moisture content was examined. Major results obtained from the study are as follows; (i) Backscattering coefficients measured by E ERS-1 AMI are not more sensitive to surface conditions than those by the scatterometer and have a high correlation with soil moisture content for the soil moisture range of less than 40 correlation with the saturation degree of soil moisture, but low sensitivity to it. (iii) Each land cover has its own seasonal change, which shows the possibility to classify land cover types from multitemporal SAR data. (iv) Using SAR data with visible satellite data, soil moisture distribution maps are made up and validated with qualitative observations.
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Huaxia YAO, Michio HASHINO, Akira TERAKAWA, Shijian CHEN
1997 Volume 10 Issue 6 Pages
607-616
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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Groundwater dynamics and water budget characteristics of plain farmland are studied in the Xin-Xing-Yuan Agricultural Experiment Site of 6.8 km2 in Hubei Province of China, to analyze complex relations of inflow and outflow and the effects of agricultural activities. Groundwater level data is collected by two year (1993-1994) field monitoring, and its changes in time and space are discussed. Analyses of water budgets of daily, monthly and annual periods are implemented for sections with different crop and cultivation style. Monthly groundwater change and net outflow (drainage or irrigation) have no clear patterns because of changeable rainfall and artificial management activity. And monthly budgets differ between lower section of rice field and higher section of vegetable field. However, annual water budgets show a similar pattern that groundwater storage loses a little and water drainage behaves as the main outflow, which is determined by requirements of farm management. Furthermore irrigation-drainage option is proposed to approach upon more efficient water management in the lowland farms.
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Yasuto TACHIKAWA, Yutaka ICHIKAWA, Michiharu SHIIBA
1997 Volume 10 Issue 6 Pages
617-626
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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The storage function method developed by Kimura is often used for short-term runoff simulation, and some on-line prediction methods coupling with the storage function method and Kalman filtering which aims to update forecasts, have been developed by several investigators including the authors. In this paper, the frameworks of a flood runoff prediction method and a treatment of uncertainty of model parameters in the storage function method are newly devised. In the new method, a number of filters with different parameters are run simultaneously, and the probability distribution assigned to these filters is updated by using Kalman filtering with real-time observation data. The application results show that the new treatment enhances the prediction accuracy.
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Akihiko KONDOH, Jun SHIMADA
1997 Volume 10 Issue 6 Pages
627-629
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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1997 Volume 10 Issue 6 Pages
635-636
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
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[in Japanese], [in Japanese]
1997 Volume 10 Issue 6 Pages
637
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
JOURNAL
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[in Japanese]
1997 Volume 10 Issue 6 Pages
640
Published: November 05, 1997
Released on J-STAGE: October 22, 2009
JOURNAL
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